Polymer fused batteries

ABSTRACT

Polymer-fused batteries are provided. The battery includes a casing, an anode coupled to the casing, an electrical source disposed between the casing and the anode, and a fuse. The polymer fuse comprises an electrically-conductive material formulated to decompose upon contact with a bodily fluid.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.13/365,762, filed on Feb. 3, 2012.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to batteries, and inparticular, to button style batteries.

2. Description of the Related Art

Batteries are employed as electrical sources for use in portable devicesthat utilize electricity to function. As such, there is often strongmotivation to make batteries as small as possible while still providingthe necessary high current density. Li/ion batteries, for example, areideally suited for this application as they are capable of a highcurrent density while providing exemplary small form factors includingbutton style, coin style, and disk style batteries. These batteries canbe extremely useful because of their ability to provide a current sourcewithout taking up much space and being quite light. As a consequence,these batteries allow for smaller and lighter devices to be createdwhich can provide considerable utility to a user.

Such batteries are often used in devices where size and weight isimportant. For example, batteries having one of these small form factorsare often used in such devices as watches, calculators, or even musicalgift cards where a larger battery may defeat the purpose or utility ofsuch a device. In addition, these batteries are often used as reservepower for numerous larger devices. For example, button, coin, or diskstyle batteries are often used in computers to maintain an internalclock or BIOS memory in the case of loss of power or unplugging of thecomputer from an outside power source. Because of their general utility,these small form factor batteries have become ubiquitous.

SUMMARY OF THE INVENTION

Unfortunately, the advantages of small form factor batteries is somewhatdiminished by their danger to children. Due to their small form factor,these batteries are often swallowed by children and can become lodged invarious parts of a child's body. Consequently, severe danger or death tothe child may result. In particular, when lodged within the body, acharged battery will induce a current to the surrounding tissue, whichmay damage that affected tissue.

An improved battery has been provided that incorporates the utility ofsmall form factor batteries while decreasing the risks of harm in theform of current-induced tissue damage in the event of swallowing by anadult or child. The improved battery provides features that protectagainst current flow that may be induced if ingested.

In an embodiment, by way of example only, the battery includes a casing,an anode coupled to the casing, an electrical source disposed betweenthe casing and the anode, and a polymer fuse. The polymer fuse comprisesan electrically-conductive material, the material becomingnon-conductive upon contact with a suitable bodily fluid thus renderingthe battery essentially non-functional.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the invention will be readilyunderstood, a more particular description of the invention brieflydescribed above will be rendered by reference to specific embodimentsthat are illustrated in the appended drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered to be limiting of its scope, the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings, in which:

FIG. 1 is a cutaway view of a battery, according to one embodiment ofthe present invention;

FIG. 2 is a cutaway view of a battery, according to another embodimentof the present invention;

FIG. 3 is a cutaway view of a battery, according to still anotherembodiment of the present invention; and

FIG. 4 is a flow diagram of a method of manufacturing a battery,according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The illustrated embodiments below provide a battery that reduces alikelihood of tissue damage and/or death if ingested. Generally, thebattery includes a casing, an anode coupled to the casing, an electricalsource disposed between the casing and the anode, and a polymer fuseover at least a portion of the anode. The polymer fuse comprises anelectrically-conductive material formulated to provide electricalcommunication between the anode cap and the electrical source, thematerial becoming non-conductive upon contact with a suitable bodilyfluid thus rendering the battery essentially non-functional. Theaforementioned battery can have small form factors include button style,coin style, or disk style batteries.

FIG. 1 is a cutaway view of a battery 100, according to an embodiment.The battery 100 has a button style form factor. The battery 100 isdepicted as resting on a lower end (not visible) with visible upper endand sides of the battery. In an embodiment, the battery 100 has asubstantially cylindrical shape with a shorter height than diameter,similar to a button, disk or coin. As used herein, the terms “buttonbattery,” “button form factor,” and “button style battery” are used todescribe batteries having any of the button, disk, or coin style formfactors. It will be understood by one skilled in the art in light of thepresent disclosure that the form factors depicted herein are exemplaryonly and can vary considerably without departing from the scope of thepresent invention.

According to one embodiment, the battery 100 includes dimensions thatmeet one or more battery dimension standards. For example, standardsetting organizations create dimension standards for batteries such thatbatteries made by different manufactures can be made to conform to thedimension standards. Consumers may then be able to interchange batteriesfrom different manufacturers in a single device.

With reference to FIG. 1, the battery 100 includes a casing 102, anelectrical source 104, and a polymer fuse 106. The battery 100 isdepicted with substantially circular and flat upper and lower ends. Inan embodiment, the casing 102 provides a structural support for othercomponents of the battery 100 and includes a planar plate 110 and asidewall 112. The planar plate 110 defines a lower end of the battery100, and the sidewall 112 extends from an outer diameter of the exposedplanar plate 110 to form a side of the button style battery 100. Inaccordance with an embodiment, the sidewall 112 is formed substantiallyperpendicular to the planar plate 110 and has a lip portion 114 thatprotrudes radially inwardly a distance to define an open top 116.

The casing 102 is formed from a wide variety of materials. In oneembodiment, the casing 102 is formed from a single material, such as anelectrical conductor or an electrical insulator. According to anotherembodiment, the casing 102 includes one or more materials such as anelectrical conductor and an electrical insulator. According to oneembodiment, at least a portion of the casing 102 includes a conductor,which acts as a terminal of the battery 100.

The electrical source 104 includes an anode 120, a cathode 122, and aseparator 124. The electrical source 104 may be any type of electricalsource known in the art. Often, electrical sources within batteriesinclude one or more electrochemical cells, which act as the anode 120and the cathode 122 and convert chemical energy into electricity.Exemplary types of electrochemical cells include, but are not limitedto, lithium ion, alkaline, zinc-carbon, nickel-cadmium, silver oxide,lithium, or any other electrochemical electrical source known in theart. One of skill in the art will recognize the considerable variationof materials and configurations for the electrical source 104 well knownin the art and that the present disclosure embraces use of any of thesematerials or configurations within its scope.

The anode 120 and the cathode 122 are generally substantially similarlyshaped. For example, as illustrated in FIG. 1, the anode 120 and thecathode 122 are disk-shaped. In an embodiment, the anode 120 and cathode122 have substantially equal diameters. In alternate embodiments, theanode 120 is larger than the cathode 122, or vice versa. Although theanode 120 is shown as having a greater thickness than the cathode 122,the cathode 122 is thicker than the anode 120 in other embodiments.

The separator 124 maintains the anode 120 and cathode 122 separate fromeach other to prevent short circuits while still allowing ionictransport from the anode 120 to the cathode 122. In an embodiment, theseparator 124 envelops and maintains the cathode 122 apart from theanode 120. For example, the separator 124 positions the cathode 122against an interior surface of the planar plate 110 of the case 102.Suitable materials from which the separator 124 is formed include, butare not limited to, silicones, polystyrenes, polyethylenes, nylons,teflons and the like.

According to an embodiment, the separator 124 has a planar member 126and a side member 128. The planar member 126 is disposed between theanode 120 and the cathode 122 and is dimensioned to extend oversubstantially an entirety of an upper surface of the cathode 122. Theside member 128 extends axially from the planar member 126 toward theplanar plate 110 to surround a side surface of the cathode 122.

The polymer fuse 106 is disposed over the electrical source 130 and isconfigured to render the battery 100 inoperable, when the battery 100 isswallowed or in contact with a bodily fluid. In an embodiment, thepolymer fuse 106 is formed over the anode 120. According to anotherembodiment, the polymer fuse 106 includes a planar portion 130, a sideportion 132, and an attachment flange 134. The planar portion 130 isdisposed continuously over and is in contact with the anode 120, and theside portion 132, which extends axially from the planar portion 130,continuously surrounds a side surface of the anode 120 and contacts theseparator 124. To retain the polymer fuse 106 within the casing 102, theattachment flange 134 extends from the side portion 132 and isconfigured to be inserted into a gasket 142 disposed in the casing 112.More particularly, the gasket 142 has a groove 144 defined between aninner wall 146 and an outer wall 148, and the attachment flange 134 isinserted into the groove 144.

In an embodiment, the polymer fuse 106 comprises anelectrically-conductive material formulated to allow electricity to beconducted to the anode 120 when the polymer fuse 106 is intact, but tobe rendered non-conductive as described above upon contact with thebodily fluid. According to an embodiment, the electrically-conductivematerial comprises a block copolymer formulated to at least partiallydecompose in caustic and/or acidic environments. The block copolymerincludes a hydrophobic block and a hydrophilic block. As used herein,the term “block copolymer” is a copolymer that comprises more than onespecies of monomer, wherein the monomers are present in homogenouslarger units or blocks. Each block of the specific monomer comprisesrepeating sequences of only that monomer, uninterrupted by othermonomers. The term “monomer,” as used herein, is defined as a moleculethat can undergo polymerization thereby contributing constitutionalunits to the essential structure of a macromolecule, an oligomer, ablock, a chain and the like. The term “polymer,” as used herein, is amacromolecule comprising multiple repeating smaller units or molecules(monomers) bonded together covalently. The polymer may be a naturalpolymer or a semi-synthetic polymer or a fully synthetic polymer. Theterm “copolymer,” as used herein is a polymer derived from more than onechemical species of smaller unit or monomer. The monomers of the blockcopolymer may be used individually and in combinations thereof inaccordance with the method of the present invention.

The hydrophobic block is formulated to provide a matrix for theconductive block such that, upon exposure to suitable bodily fluids andsubsequent decomposition of the conductive block, as described below,the overall polymer superstructure is retained. In an embodiment, thehydrophobic block comprises a polystyrene chain including an R-group. Inan example, the polystyrene chain has the following formula:

wherein R is selected from a group consisting of hydrogen, methyl, andtrifluoromethyl, and n is an integer from 0 to 500. One of skill in theart will recognize the considerable variation of materials available forthe hydrophobic block.

In another embodiment, the hydrophilic block comprises another materialthat is conductive and that is capable of undergoing self-assembly intodiscrete domains in the presence of the hydrophobic block.

The hydrophilic block is formulated to provide a vehicle forincorporation of metal nanoparticles into the polymer fuse whilesimultaneously providing a mechanism by which said nanoparticles couldbe released from the polymer fuse upon exposure to suitable bodilyfluids.

In an embodiment, the hydrophilic block comprises a functionalizedpolyacrylate having the following formula:

whereinR is selected from a group consisting of hydrogen, methyl, andtrifluoromethyl,n is an integer from 0 to 500, andX is a 2-pyridyl pendant group.

In an embodiment, the 2-pyridyl pendant group has the following formula:

wherein the R′-group of the 2-pyridyl pendant group represents theconnectivity to the acrylate ester. In another embodiment, the R′-groupof the 2-pyridyl pendant group also further includes one or moreadditional groups selected from a group consisting of methyl andhaloalkane. The haloalkane comprises fluorine, in an embodiment. Forexample, the haloalkane is a trifluoromethyl. In another embodiment, thehaloalkane includes a different halide. In an example, the one or moreadditional groups have one of the following formulas:

In accordance with another embodiment, the 2-pyridyl pendant group hasthe following formula:

wherein Y is selected from a group consisting of hydrogen and methyl,and Z is selected from a group consisting of hydrogen and methyl andwherein Y and Z can be connected to form a ring.

In still other embodiments, the electrically-conductive materialcomprises a different polymer that is conductive by virtue ofcoordinated metal salts. Such material is selected or is formulated tohave sensitivity to aqueous environments and/or pH that are similar tothose provided in a child or adult person. The electrically-conductivematerial comprises non-polymeric material, in other embodiments. Forexample, the electrically-conductive material comprises a starch dopedwith lithium salts. In another example, other conductive materials areemployed.

The polymer fuse 106 is a separate component that is positioned over theelectrical source 104, in an embodiment. For example, the polymer fuse106 can be separately formed and then coupled to the battery 100 via thegasket 142. In another embodiment, the polymer fuse 106 is a coatingformed over the electrical source 104. In alternate embodiments, thepolymer fuse 106 has a different configuration. Although the polymerfuse 106 is illustrated as being disposed over and in contact with theanode 120, it will be appreciated that the polymer fuse 106 is disposedover and in contact with the cathode 122 in alternate embodiments. Topreserve structural integrity of the polymer fuse 106 during operationand/or handling, a protective grid 150 is disposed over the polymer fuse106. The protective grid 150 has a mesh configuration and is sized to bedisposed over a majority of an exposed surface of the polymer fuse 106.In one example, the protective grid 150 has an outer diameter that issubstantially equal to that of the planar portion 130 of the polymerfuse 106. Alternatively, the protective grid 150 is smaller in diameterthan the planar portion 130 of the polymer fuse 106, and/or theprotective grid 150 is a disk, plate or another configuration havingopenings there through. According to an embodiment, materials suitablefor forming the protective grid 150 include but are not limited to aconductive metal such a chromed iron, copper, or stainless steel. Inother embodiments, other suitable conductive materials are used to formthe protective grid 150.

FIG. 2 is a cutaway view of a battery 200, according to anotherembodiment. The battery 200 is a button-style battery and includes acasing 202, an electrical source 204, a fuse 206, and an anode cap 208.Here, the casing 202 is formed substantially similar to casing 102 ofFIG. 1, and an anode 220, a cathode 222, and a separator 224 of theelectrical source 204 are formed substantially similar to anode 120,cathode 122, and separator 124 of FIG. 1.

The anode cap 208 is disposed over the anode 220 and over an open top216 of the casing 202. In an embodiment, the anode cap 208 has a planarportion 260 and a sidewall 262. The planar portion 260 is disk-shapedand contacts the anode 220, and the sidewall 262 of the anode cap 208extends from an outer periphery of the planar portion 260 at an angletowards the casing 202. In an embodiment, an attachment portion 264 ofthe sidewall 262 of the anode cap 208 is configured to be inserted intoa gasket 242 disposed in the casing 202. More particularly, the gasket242 has a groove 244 defined between an inner wall 246 and an outer wall248, and the attachment portion 264 is inserted into the groove 244.

The anode cap 208 is made from a material similar to that used for thecasing 202. For example, the anode cap 208 is an electrical conductor oran electrical insulator. According to another embodiment, the anode cap208 includes one or more materials such as an electrical conductor andan electrical insulator. According to one embodiment, at least a portionof the anode cap 208 includes a conductor, which acts as a terminal ofthe battery 100.

According to one embodiment, both the anode cap 208 and the casing 202each act as terminals on the battery 200. In an embodiment, the anodecap 208 acts as a positive terminal while the casing 202 acts asnegative terminal of the battery 200, or vice versa. In one embodiment,the casing 202 acts as an end terminal in that electrical connectionwith the battery 200 may be created with the end of the battery, forexample the lower end of the battery 200 that is not visible in FIG. 2.In one embodiment, the casing 202 may act as a side terminal in thatelectrical connection with the battery 200 may be created on the side ofthe battery.

The polymer fuse 206 is disposed over the anode cap 208 and allowselectricity to be conducted to the anode cap 208 when the polymer fuse206 is intact, but to decompose as described elsewhere upon contact withthe bodily fluid. Here, the polymer fuse 206 is formed of substantiallythe same material as described in relation to fuse 106 of FIG. 1. Thepolymer fuse 206 is formed as a coating over the anode cap 208 in FIG.2, but can have a different configuration in another embodiment. Forexample, the polymer fuse 206 is a separate component that is overlayedonto the anode cap 208.

FIG. 3 is a cutaway view of a battery 300, according to anotherembodiment. The battery 300 is a button-style battery and includes acasing 302, an electrical source 304, a fuse 306, and an anode cap 308formed substantially similar to casing 102, 202, electrical source 104,204, and fuse 106 and 206 of FIGS. 1 and 2, and anode cap 208 of FIG. 2.Battery 300 also includes a protective grid 350 disposed over thepolymer fuse 306. The protective grid 350 is formed substantiallysimilar to protective grid 150 of FIG. 1.

FIG. 4 is a flow diagram of a method 400 of forming a battery (e.g.,battery 100, 200, 300), according to an embodiment. In an example, anelectrical source (e.g., an anode 120, 220 and a cathode 122, 222), aseparator (e.g., separator 124, 224) and a gasket (e.g., gasket 142,242) are disposed in a casing (e.g., casing 102, 202, 302), step 402. Inan embodiment, a portion of the anode of the electrical source isinserted into the gasket. In another embodiment, the battery is anoff-the-shelf battery including an anode cap (e.g., anode cap 208)disposed over the anode. Outer edges of the anode cap are disposed in agroove of the gasket.

Next, a polymer fuse is placed over the electrical source, step 404.According to an embodiment, the polymer fuse (e.g., fuse 106, 206, 306)comprises an electrically-conductive material made up of a blockcopolymer similar to that described above. The block copolymer isinitially formed by a standard Living Polymerization technique, such asRAFT (Reversible Addition-Fragmentation Chain Transfer polymerization),ATRP (Atom Transfer Radical Polymerization), or another process known tothose skilled in the art for forming block copolymers. For example, oneor more monomers suitable for forming selected hydrophobic blocks andselected hydrophilic blocks are processed to form the block copolymer.In an embodiment, the hydrophobic and hydrophilic blocks self-assembleto form a pattern.

After the electrically-conductive material is formed, the material issuitably dimensioned and configured into a fuse having dimensions and ashape similar to fuse 106, 206, or 306 and the polymer fuse is disposedover the electrical source, in an embodiment. In accordance with anembodiment in which the battery omits an anode cap, the polymer fuse ispositioned over the anode. An attachment flange, which may be includedon the polymer fuse, is inserted into the groove of the gasket tomaintain the polymer fuse in position over the anode. In anotherembodiment in which the battery includes the anode cap, theelectrically-conductive material is spin-applied over the anode cap toform the polymer fuse. In other embodiments, the electrically-conductivematerial is applied in a different manner to form a coating over theanode cap.

Optionally, a protective grid is positioned over the polymer fuse, step406. According to an embodiment, a protective grid (e.g., protectivegrid 150, 350) is pre-formed and suitably dimensioned to be positionedover the anode or anode cap. In particular, the protective grid is awire mesh or mesh material comprising a conductive material similar tothat described in conjunction with protective grid 150, and the meshmaterial is formed into a suitable shape. The mesh is then placed overthe polymer fuse and press fit into the electrically-conductivematerial. In an embodiment, fastening mechanisms or adhesives areemployed to hold the mesh in position over the polymer fuse.

During normal operation, the polymer fuse 106, 206 is intact and allowscurrent to flow from one terminal of the battery 100, 200, 300 toanother. In an event in which the battery 100, 200, 300 is swallowed orcomes into contact with bodily fluids, the polymer fuse 106, 206 beginsto decompose in a manner designed to render the polymer fusenon-conductive. For example, the electrically-conductive portion of thepolymer fuse 106, 206 reacts with the bodily fluid and the polymer fuse106, 206 loses structural integrity. As a result, theelectrically-conductive portion of the polymer fuse disintegrates sothat the polymer fuse 106, 206 becomes non-conductive and preventscurrent flow between the battery terminals.

In an example, the polymer fuse material comprises a block copolymercomprising polystyrene and a polyacrylate having a pendant 2-pyridylmoiety coordinated with a metallic entity. Should the battery becomelodged in a body part of a child or adult, a caustic environment may beset up by a runaway current flow between the battery terminals throughsurrounding tissue thus degrading an ester linkage of the 2-pyridylmoiety to render the block copolymer non-conductive and the batteryinoperable. If the battery is lodged in a stomach of the child or adult,an acid environment of the stomach inactivates the coordinatingproperties of the 2-pyridyl moiety to render the block copolymernon-conductive and the battery inoperable. Further, in an embodimentdescribed above wherein the pendant 2-pyridyl moiety is linked to thepolymer backbone via an acetal linkage, the acid environment of thestomach serves to decompose said acetal thus rendering the blockcopolymer non-conductive and the battery inoperable.

An improved battery has now been provided that allows for the utility ofsmall form factor batteries, but also decreases the risks of harm incase of swallowing by an adult or child. By including a polymer fuse106, 206, 306 in the form of a coating or overlay, the battery size isslightly increased relative to conventional small form factor batteries.Conventional small form factor batteries can be retrofitted with thepolymer fuse 106, 206, 306 to provide the improved battery.Additionally, forming the polymer fuse 106, 206, 306 fromelectrically-conductive material that disintegrates when contacted withbodily fluids insures that current flow between the battery terminals isprevented to hereby render the battery inoperable when in the child's oradult's body. Moreover, the electrically-conductive material can betailored to react with bodily fluids of a selected pH or composition tothereby target circumstances under which the polymer fuse disintegratesand renders the battery inoperable.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or embodiments described herein are not intended tolimit the scope, applicability, or configuration of the claimed subjectmatter in any way. Rather, the foregoing detailed description willprovide those skilled in the art with a convenient road map forimplementing the described embodiment or embodiments. It should beunderstood that various changes can be made in the function andarrangement of elements without departing from the scope defined by theclaims, which includes known equivalents and foreseeable equivalents atthe time of filing this patent application.

What is claimed is:
 1. A battery comprising: a casing; an anode coupled to the casing; an electrical source disposed between the casing and the anode; and a polymer fuse comprising an electrically-conductive material, said material becoming non-conductive upon contact with a bodily fluid.
 2. The battery of claim 1, wherein the polymer fuse is over at least a portion of the anode, and the electrically-conductive material comprises a block copolymer including a hydrophobic block and a hydrophilic block formulated to provide electrical communication between the anode and the electrical source.
 3. The battery of claim 2, wherein the hydrophobic block has a Formula I:

wherein R is selected from a group consisting of hydrogen, methyl, and trifluoromethyl, and n is an integer from 1 to
 500. 4. The battery of claim 3, wherein the hydrophilic block includes an acrylate ester and has a Formula II:

wherein R is selected from a group consisting of hydrogen, methyl, and trifluoromethyl, n is an integer from 1 to 500, and X is a 2-pyridyl pendant group.
 5. The battery of claim 4, wherein the 2-pyridyl pendant group has Formula III:

and R′ represents the connectivity to the acrylate ester.
 6. The battery of claim 5, wherein: the 2-pyridyl pendant group further includes one or more groups selected from a group consisting of methyl and haloalkane.
 7. The battery of claim 6, wherein the 2-pyridyl pendant group is selected from a group consisting of


8. The battery of claim 4, wherein: X is

Y is selected from a group consisting of hydrogen and methyl, and Z is selected from a group consisting of hydrogen and methyl, and Y and Z can be connected to form a ring.
 9. The battery of claim 1, further comprising an anode cap disposed over the anode, wherein the polymer fuse is formed over the anode cap.
 10. The battery of claim 1, further comprising a grid disposed over the polymer fuse.
 11. The battery of claim 10, wherein the grid comprises a conductive material.
 12. The battery of claim 11, wherein the conductive material comprises a material selected from a group consisting of chromed iron, copper, and stainless steel.
 13. A battery comprising: a casing; an anode coupled to the casing; an anode cap coupled to the casing and anode; an electrical source disposed between the casing and the anode cap; a polymer fuse over at least a portion of the anode cap, the polymer fuse comprising an electrically-conductive material formulated to at least partially decompose upon contact with a bodily fluid and to provide electrical communication between the anode cap and the electrical source when the polymer fuse is intact; and a protective grid disposed on the polymer fuse.
 14. The battery of claim 13, wherein the polymer fuse is over at least a portion of the anode, and the electrically-conductive material comprises a block copolymer including a hydrophobic block and a hydrophilic block formulated to provide electrical communication between the anode and the electrical source.
 15. The battery of claim 13, wherein: the hydrophobic block has a Formula I:

wherein R is selected from a group consisting of hydrogen, methyl, and trifluoromethyl, and n is an integer from 1 to 500, and the hydrophilic block has a Formula II:

wherein R is selected from a group consisting of hydrogen, methyl, and trifluoromethyl, n is an integer from 0 to 500, and X is a 2-pyridyl pendant group.
 16. A method of manufacturing a battery comprising: providing a casing, an anode coupled to the casing, and an electrical source disposed between the casing and the anode; and forming a polymer fuse, the polymer fuse comprising an electrically-conductive material formulated to at least partially decompose upon contact with a bodily fluid.
 17. The method of claim 16, wherein the step of providing comprises providing an anode cap over the anode, the anode cap coupled to the casing, and the step of forming a polymer fuse comprises coating the anode cap with the electrically-conductive material to provide electrical communication between the anode and the electrical source when the polymer fuse is intact.
 18. The method of claim 17, further comprising placing a protective grid over the polymer fuse.
 19. The method of claim 16, wherein the electrically-conductive material comprises a block copolymer material including a hydrophobic block and a hydrophilic block.
 20. The method of claim 17, wherein the step of forming includes spin-applying the polymer fuse over the anode cap.
 21. The method of claim 19, wherein the step of forming includes self-assembling the block copolymer material by implementing a standard curing technique. 